OMIM ID:
Aland Island Eye Disease
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
This is an X-linked disorder in which males have a variety of ocular defects. The fundus is hypopigmented and the fovea is incompletely developed. The hypopigmentation is most pronounced in the posterior pole and peripapillary region. Variable degrees of iris transillumination have also been noted. Progressive axial myopia, nystagmus, astigmatism, defective night vision, and a protan color vision defect are additional cardinal features. Females may be mildly affected with subtle nystagmus and color vision defects. It is sometimes mislabeled as X-linked albinism (OA1, #300500) but differs importantly from that disorder by the lack of misrouting of optic nerve axons. The eponymic label ‘Forsius-Eriksson type ocular albinism’ further adds to the confusion with ocular albinism.
Systemic Features
No systemic abnormalities have been reported.
Genetics
Inheritance
This is an X-linked disorder resulting from a mutation in the CACNA1F gene located at Xp11.23. Molecular DNA studies suggest that there may be some heterogeneity in the causative mutations but in the original family reported by Forsius and Eriksson, a 425-bp deletion in the CACNA1F gene has been found to segregate as expected in the phenotypes. The highly variable and subtle nature of clinical manifestations in females limits their usefulness in determination of carrier status and genotyping is necessary.
The CSNB2A type of congenital stationary night blindness (300071) is caused by mutations in the same gene suggesting allelism of the two disorders. Aland Island eye disease shares some clinical features such as night blindness and occasionally mild color vision defects but differs in the presence of progressive myopia and an abnormal fovea.
Pedigree
X-linked recessive, carrier mother
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked recessive, father affected
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.